The present invention relates to a system, device and method for obtaining data pertaining to the stress state of a plant and its environment and for displaying such data in a readily interpretable manner. More particularly, the present invention relates to a system and method which incorporate a detector device for determining the boundary diffusion layer resistance in an environment in which a plant is cultivated, such that accurate estimation of evapo-transpiration of the plant can be effected.
Cultivation of commercial crops depends on the monitoring of the hydration of a plant or field. Maintaining the correct hydration, which is dependent on several factors including irrigation scheduling and the like is crucial for the proper development of plants and as such, precise monitoring of the hydration, at any given stage of development is advantageous.
In the past growers have mainly relied on their intuition and expertise in assessing crop hydration conditions. This expertise relied mainly on crop and soil inspection and observing the environmental conditions in which the crop was cultivated. One working assumption often relied upon, was that evaporation equals precipitation. Although this method was generally successful in predicting the condition of the crop field, it was time consuming and inaccurate mainly since the growth conditions in a field vary from one area to another. Furthermore, experience gained by a grower cultivating a certain crop under certain conditions could not be recorded or analyzed and as such was not applicable to other crops or other cultivation conditions.
The need for a more precise method with which a grower can monitor the hydration and stress of a plant has led to several solutions.
One such solution involves the use of a pan for monitoring the evaporation (Ep) of water therefrom in a specific environment. Such a pan is placed in a field or greenhouse in which the plants cultivated are to be monitored. The evaporation data collected can be converted to evapo-transpiration (Et) data of the plants by the use of correction factors which vary from 0.5 to 0.85 (Et/Ep) depending on the climatic and crop conditions.
Although this method presents a significant improvement to the above practice, it still lacks accuracy. In addition, the pan employed requires regular maintenance such as keeping the water clean, etc. Furthermore, this method is difficult to automate, and is not detective enough to small changes in the plant or environment.
In recent years, in an effort to overcome the limitations inherent to the system and methods described above, growers have increasingly utilized systems and devices which include arrays of precise detectors for measuring the temperature and humidity and other related parameters of the environment and/or soil proximal to the cultivated plants.
The advent of such precise monitoring technologies and methodologies enabled growers to track and record changes in a field or greenhouse enabling close monitoring, in some cases, of a single plant.
The information recorded is analyzed and the resultant data incorporated into a plant hydration profile, such a profile can then be used to assess crop condition and development through daily and seasonal changes. For further details see, for example, Wolf, B. Diagnostic Technique for Improving Crop Production. Haworth Press. P.185-187.
Numerous models exist and are presently in use for analyzing the collected data from monitored plants, examples include, but are not limited to, the Hargraves equation and the Harmon equation (for reference see, Shuttleworth, W. J. 1993, Evaporation Ch. 4 In D. R. Maidment (ed.) Handbook of Hydrology, Mcgraw-Hill, which is incorporated herein by reference). The major difference between these various models is derived from the type of data collected. One of the accurate and most commonly used model is the Penman equation (Greenhouse climate control: an integrated approach. J. C. Bakker, G. P. A. Bot, H. Challa, N. J. Van de Braak, Eds. Wageningen Press, Wageningen, 1995, p. 143). The Penman equation can be expressed as follows:                     LE        =                                            s                              s                +                γ                                      ⁢                          R              n                                +                                                                      ρ                  a                                ⁢                                  C                  a                                                            r                b                                      ⁢                          D                              s                +                γ                                                                        (                  Equation          ⁢                      xe2x80x83                    ⁢          1                )            
where E is the evaporative water flux density (kg mxe2x88x922sxe2x88x921); L is the heat of evaporation (J kgxe2x88x921); s is the slope of the saturated vapor pressure curve (Pa Kxe2x88x921); xcex3 is the thermodynamic psychrometric constant (Pa Kxe2x88x921); Rn is the net radiation (W mxe2x88x922); xcfx81a is the air density (kg mxe2x88x923); Ca is the specific air heat (J kgxe2x88x921sxe2x88x921); D is the vapor pressure saturation deficit (Pa); and rb is the boundary diffusion layer resistance (s mxe2x88x921).
According to the Penman equation and other similar models, the rate of evapo-transpiration from a plant is resolved by incorporating data from several detectors/sensors such as of humidity and temperature into an equation. However, in plant leaves and for that matter any other evaporative surfaces, there exists a layer of humidified air which drastically decreases the evapo-transpiration from such a surface. This layer is known as the boundary diffusion layer, and the effect thereof on evapo-transpiration is termed the boundary diffusion layer resistance (rh). Since this effect drastically decreases the evapo-transpiration from a plant, precluding this parameter when calculating an evapo-transpiration rate from a plant often results in an erroneous hydration data.
Presently, there exists no system or method which employ an accurate detector for determining the boundary diffusion layer resistance of a given environment. As such, data collected from a plant cultivated in a field or a greenhouse is often processed with a disregard to this parameter. Such omission of data pertaining to this important parameter, often leads to an erroneous cultivar hydration profile and as such to great losses in crops.
In addition, the data provided to a grower utilizing present day systems and methods is presented as numerical data. Such presentation can often be difficult to perceive and analyze and as such requires an experienced operator to decipher.
There is thus a widely recognized need for, and it would be highly advantageous to have, a method and system for measuring and displaying the stress state of a plant which is devoid of the above limitations of the prior art.
According to one aspect of the present invention there is provided a system for co-displaying a state of a plant and its environment, the system comprising (a) at least one environment detector for monitoring at least one parameter of the plant""s environment; (b) at least one canopy detector for monitoring at least one parameter of the plant itself; (c) a processor for processing the at least one parameter of the plant""s environment and the at least one parameter of the plant itself for obtaining at least one processed parameter of the plant""s environment and at least one processed parameter of the plant itself; and (d) a display for co-displaying the at least one processed parameter of the plant""s environment and the at least one processed parameter of the plant itself, such that each of the at least one processed parameter of the plant""s environment is realized by a first displayed area of a first color selected among at least two first colors, wherein each of the at least two first colors represents a range of the at least one parameter of the plant""s environment, and further such that each of the at least one processed parameter of the plant itself is realized by a second displayed area of a second color selected among at least two second colors, wherein each of the at least two second colors represents a range of the at least one parameter of the plant itself.
According to another aspect of the present invention there is provided a method for displaying a state of a plant and it""s environment, the method comprising the steps of (a) monitoring at least one parameter of the plant""s environment; (b) monitoring at least one parameter of the plant itself; (c) processing the at least one parameter of the plant""s environment and the at least one parameter of the plant itself for obtaining at least one processed parameter of the plant""s environment and at least one processed parameter of the plant itself; and (d) co-displaying the at least one processed parameter of the plant""s environment and the at least one processed parameter of the plant itself, such that each of the at least one processed parameter of the plant""s environment is realized by a first displayed area of a first color selected among at least two first colors, wherein each of the at least two first colors represents a range of the at least one parameter of the plant""s environment, and further such that each of the at least one processed parameter of the plant itself is realized by a second displayed area of a second color selected among at least two second colors, wherein each of the at least two second colors represents a range of the at least one parameter of the plant""s itself.
According to further features in preferred embodiments of the invention described below, each of the first color and the second color is independently selected from the group consisting of a red color, a green color and a yellow color.
According to still further features in the described preferred embodiments the at least one environment detector and the at least one canopy detector detect a parameter of the same nature.
According to still further features in the described preferred embodiments the at least one environment detector is selected from the group consisting of an air humidity detector, an air temperature detector, a boundary diffusion layer resistance detector, a solar radiation detector, a soil moisture detector and a soil temperature detector.
According to still further features in the described preferred embodiments the at least one canopy detector is selected from the group consisting of a leaf temperature detector, a flower temperature detector, a fruit surface temperature detector, a stem flux relative rate detector, a stem diameter variation detector, a fruit growth rate detector and a leaf CO2 exchange detector.
According to still further features in the described preferred embodiments the display is selected from the group consisting of a computer screen display, a monitor display, an image projector and a printer.
According to yet another aspect of the present invention there is provided a system for estimating evapo-transpiration from a plant, the system comprising (a) a first detector for detecting environmental radiation at a vicinity of the plant; (b) a second detector for detecting air humidity at a vicinity of the plant; (c) a third detector for detecting air temperature at a vicinity of the plant; (d) a fourth detector for detecting boundary diffusion layer resistance at a vicinity of the plant; and (e) a processor communicating with the first, second third and fourth detectors for retrieving data from the first, second third and fourth detectors and for calculating, based on the data a value corresponding to the evapo-transpiration from the plant.
According to still another aspect of the present invention there is provided a method of estimating evapo-transpiration from a plant, the method comprising the steps of collecting values corresponding to an environmental radiation, an air humidity, an air temperature and a boundary diffusion layer resistance at a vicinity of the plant and using the values for calculating a value corresponding to the evapo-transpiration from the plant.
According to further features in preferred embodiments of the invention described below, the first, second and third detectors are used for obtaining a slope of the saturated vapor pressure curve, a net radiation, an air density, a specific air heat and a vapor pressure saturation deficit.
According to still further features in the described preferred embodiments the value corresponding to the evapo-transpiration from the slant (LE) is determined by:   LE  =                    s                  s          +          γ                    ⁢              R        n              +                                        ρ            a                    ⁢                      C            a                                    r          b                    ⁢              D                  s          +          γ                    
where E is the evaporative water flux density (kg mxe2x88x922sxe2x88x921); L is the heat of evaporation (J kgxe2x88x921); s is the slope of the saturated vapor pressure curve (Pa Kxe2x88x921); xcex3 is a thermodynamic psychrometric constant (Pa Kxe2x88x921); Rn is the net radiation (W mxe2x88x922); xcfx81a is the air density (kg mxe2x88x923); Ca is the specific air heat (J kgxe2x88x921 sxe2x88x921); D is the vapor pressure saturation deficit (Pa); and rb is the boundary diffusion layer resistance (s mxe2x88x921).
According to still further features in the described preferred embodiments the fourth detector includes (i) a first element having a first diffusion layer; (ii) a second element having a second diffusion layer and a source of thermal energy therein; and (iii) a thermocouple coupling the first element and the second element; wherein, when the source of thermal energy provides the second element with a quanta of thermal energy, measuring a temperature difference between each of the first and second elements and the environment and accounting for an air density and a specific air heat of the environment and further for mean flux density of available radiation of each of the first and second elements, enables to calculate the evapo-transpirative resistance of the boundary diffusion layer in the environment.
According to still further features in the described preferred embodiments the first diffusion layer of the first element and the second diffusion layer of the second element are identical, such that the mean flux density of available radiation of each of the first and second elements are identical.
According to an additional aspect of the present invention there is provided a method for measuring the evapo-transpirative resistance of a boundary diffusion layer in an environment, the method comprising the steps of (a) introducing into the environment a detector including (i) a first element having a first diffusion layer; (ii) a second element having a second diffusion layer and a source of thermal energy therein; and (iii) a thermocouple coupling the first element and the second element; (b) using the source of thermal energy for providing the second element of the detector with a quanta of thermal energy; and (c) measuring a temperature difference between each of the first and second elements and the environment and while accounting for an air density and a specific air heat of the environment and further for a mean flux density of available radiation of each of the first and second elements calculating the evapo-transpirative resistance of the boundary diffusion layer in the environment.
The present invention successfully addresses the shortcomings of the presently known configurations by providing means for determining the boundary diffusion layer resistance and thereby means for estimating the evapo-transpiration from a plant. The present invention further successfully addresses the shortcomings of the presently known configurations by providing useful means for displaying the stress of, or imposed on, the plant.